Mesh networks are a type of network in which nodes often have several functions. In addition to their primary function as a sensor, actuator, or other device, these nodes also serve as routers, helping move traffic between two other nodes in the network. Mesh networks can grow quite large, often having over 100, or in some case over 1000, nodes, many or most of which are also routers.
While mesh networks tend to be robust, since there are often multiple paths between any two nodes, there are drawbacks as well. For example, with such a large number of nodes, it becomes impractical for each node to know the most efficient path to every other node in the network. Mesh networks typically utilize one or more route discovery protocols. Regardless of the protocol used, as the number of routers in the mesh network increases, the amount of routing data that must be retained and communicated throughout the network, likewise increases.
This increased amount of router data may require the individual nodes to become more expensive, as the amount of storage required to store this information grows. This forces a design tradeoff. Either the amount of memory in each router must be increased, which increases cost, or the routers are forced to each only hold a subset of all routing information. In other words, rather than saving the next hop to every other node, an intermediate router may only save the next hop to a predetermined number of other routers. This option conserves memory space, but also serves to increase the number of route discovery messages, since some previously acquired network topology information must necessarily be purged. In other embodiments, this increased amount of router data may create more overhead messages in the network, effectively reducing the bandwidth available for useful traffic. One common method to reduce the routing information is to use source routing, where a central device maintains routing information and this information is used in the packet header. This method reduces memory requirements on the nodes in the network but increases the memory requirements on the central device, requires all messages to travel through the central device, and increases over the air message size (and therefore power consumption of the device) to include the routing information.
Therefore, it would be beneficial if there were a method to limit the number of routers in a mesh network, as this would reduce the number of route discovery messages and other overhead traffic that travels on the mesh network. It would also reduce the amount of memory needed in each node to store the routing information.